The present invention relates to kilns.
More particularly the invention concerns a roller kiln for baking ceramic or refractory material.
Roller kilns for ceramic or refractory material are rather well known in the art. Usually such a kiln comprises a housing having a long tunnel through which the material to be treated in the kiln is transported. The transport means as a rule comprise a plurality of rotatable rollers disposed one after another and transversely to the length of the tunnel. Usually the rollers are located somewhere between the upper and lower walls of the housing. It is also known to provide the upper and lower walls of the kiln with a plurality of baffles which are fixedly mounted on the walls and extend towards the corresponding opposite wall. The corresponding opposite baffles on the opposite walls are so arranged as to define a gap between them which serves as a transport path for the items to be treated. These opposite baffles compel the hot gas to engage the items to be treated more effectively between the two opposite baffles.
Such kilns have a disadvantage which resides in the fact that the baffles are fixed, that is can not be adjusted, on the walls. Due to this fact the characteristics of the gas between two opposite baffles are the same regardless of the different thickness, composition and other factors the items to be treated may have. Thus, it is to be understood that the best treatment is available only for a few types of material, while the others most likely will not be given an adequate treatment.
Moreover, it is known that the kiln usually has several compartments of treatment, such as for example a pre-heating step, a degassing step, a baking step, a cooling step, etc. Usually these steps operate with completely different temperature, and many other factors. It has been noticed that the known kilns are not satisfactory with regard to controlling and ajusting the above-mentioned steps. The problem exists due to a certain temperature inertia which occurs between two adjacent steps which operate completely different temperature processes.
There have been attempts to gradually change the temperature of different steps. However, such a solution results in unduly lengthening the kiln or slowing down the transportation speed of the items to be treated. In both cases the result was undesirably highly expensive.